IBS - Institut de Biologie Structurale - Grenoble / France

Root growth arrest, rigidity and metal stress

PELLEQUER Jean-Luc — 2023-11-01T10:27:18Z

We investigated the change in stiffness of the external primary cell wall of living Arabidopsis thaliana seedlings in the presence of metallic stress using atomic force microscopy. Results reveal for the first time the uncoupling between mechanical response (CW stiffening) and root extension arrest. Molecular synergy has also been demonstrated in the physiological response to stress, where the Aluminum stress response enhances the Iron stress response via the organic acid molecule: malate.

Kaur H, Teulon J-M, Godon C, Desnos T, Chen S-wW and Pellequer J-L (2024) Correlation between plant cell wall stiffening and root extension arrest phenotype in the combined abiotic stress of Fe and Al. Plant Cell Environ. 47:574–584.

Optimized protocol for determining plant root stiffness

PELLEQUER Jean-Luc — 2023-09-11T08:26:22Z

Stiffness plays a central role in plant cell extension. We have optimized a protocol for detecting stiffness changes on the outer epidermal cell wall of living plant roots using atomic force microscopy (AFM). A protocol provides general instructions for collecting force-distance curves and analyzing stiffness using a contact-based mechanical model. With this protocol and initial AFM training, a user is able to perform indentation experiments on 4- and 5-day-old Arabidopsis thaliana and determine stiffness properties.

Kaur H, Teulon J-M, Foucher A-E, Fenel D, Chen S-wW, Godon C, Desnos T and Pellequer J-L (2023) Measuring external primary cell wall elasticity of seedling roots using atomic force microscopy. STAR Protoc. 4: 102265.

The trimechanic theory

PELLEQUER Jean-Luc — 2023-01-10T15:27:25Z

A new version of the contact-based mechanical model with the strict application of Sneddon's principles.

The trimechanic theory is the very concept of composite nanomechanics underlying the restoring mechanism
of the material under an external compression. It provides a disentanglement of the linear and tip-shape related mechanical responses at various indentation depths.

The trimechanic theory applies to all contact-based mechanical models with a power-law force–depth relationship. The perspective of this research is that stiffness measurement will not remain at a level of global assessment, but will go further to link elastic behaviors with the substructure of the nanomaterial.

– Chen SWW, Teulon JM, Kaur H, Godon C and Pellequer JL (2023) Nano-structural stiffness measure for soft biomaterials of heterogeneous elasticity. Nanoscale Horiz. 8: 75-82. [HAL]

Nanomechanics and plant root growth

2018-08-23T13:24:42Z

Establish a link between root plant growth and cell surface elasticity

Plant growth is extremely sensitive to environmental stresses, which ultimately act on the functioning of cell walls; the relaxation or blocking of the walls allows, respectively, cell growth or its arrest. In the model plant Arabidopsis growing in vitro, we have shown that stress due to a deficiency in the nutrient phosphate "-Pi" blocks root growth very quickly and irreversibly (figure below).

If chemical bonds are responsible for stopping cell expansion, then they should rapidly modify the mechanical properties of the walls. To test this hypothesis, we used atomic force microscopy (AFM). We demonstrated an increase in cell wall stiffness in the absence of Pi in the root transition zone by nanoindentation measurements with AFM.

Finally, these results demonstrate that AFM is an excellent technique allowing a precise measurement of a rapid change in the plant root state in a living organism.

AFM measurements were performed by Christian Godon and curve analyses were performed by Jean-Marie Teulon on seedlings produced by Christian and whose seeds were provided by Thierry Desnos.

Balzergue C, Dartevelle T, Godon C, Laugier E, Meisrimler C, Teulon J-M, Creff A, Bissler M, Brouchoud C, Hagège A, Müller J, Chiarenza S, Javot H, Becuwe-Linka N, David P, Péret B, Delannoy E, Thibaud M-C, Armengaud J, Abel S, Pellequer J-L, Nussaume L and Desnos T (2017) Low phosphate activates STOP1-ALMT1 to rapidly inhibit root cell elongation. Nat. Commun. 8: 15300.

The SNAP AFM standardization procedure

2018-08-23T12:48:20Z

SNAP is a calibration procedure that allows reliable measurement of Young's elastic modulus for soft samples, such as living cells, by atomic force microscopy

Following the European COST TD1002 project that we coordinated between 2010 and 2014, a multi-site and multi-machine round-robin study has been developed to improve the quantification of the elastic Young modulus of cells. This study produced a protocol called SNAP (temporarily named Dubrovnik procedure). The essence of the protocol is to improve the calibration of AFM instruments using pre-calibrated cantilevers whose spring constants have been experimentally determined. This allows a better calibration of the photodiode sensitivity. Once the procedure is applied, variability of elasticity measurements dropped to 1% on hydrogels. Below is shown the improve results (on the right) when the protocol was applied on eukaryotic cells MDCK C11. This is typically a joint project where it is difficult to assign a participatory hierarchy. However, the major role of Hans Oberleithner in the development of this action must be emphasized, as well as the driving role of Manfred Radmacher and also of Hermann Schillers in setting up and distributing the samples for the whole group.

Schillers H, Rianna C, Schäpe J, Luque T, Doschke H, Wälte M, Uriarte JJ, Campillo N, Michanetzis GP, Bobrowska J, Dumitru A, Herruzo ET, Bovio S, Parot P, Galluzzi M, Podestà A, Puricelli L, Scheuring S, Missirlis Y, Garcia R, Odorico M, Teulon JM, Lafont F, Lekka M, Rico F, Rigato A, Pellequer J-L, Oberleithner H, Navajas D and Radmacher M (2017) Standardized Nanomechanical Atomic force microscopy Procedure (SNAP) for measuring soft and biological samples. Sci. Rep. 7: 5117.